During precision grinding operations using a superabrasive grinding wheel, it is necessary to adjust the grinding cycle of the grinding machine to accommodate gradual changes in the condition of the superabrasive wheel, such as increases in sharpness during a grinding run involving multiple workparts, from the time the wheel was last trued or dressed until the time it must be trued or dressed again. Typical superabrasive wheels are cubic boron nitride or diamond wheels.
In the past such changes in the condition of the grinding wheel have been accommodated by continuously monitoring the electrical power consumed by the grinding wheel drive motor, and inputting signals from a watts transducer used to monitor electrical drive motor power consumption into the microprocessor of the machine CNC control unit which continuously automatically controls and varies the wheel infeed rate so as to keep the wheel drive motor consumption essentially constant. However, in certain applications, continuous monitoring of motor power consumption and varying of wheel infeed rate has not provided acceptable infeed control, especially when an in-process size gage is employed during grinding or when the response speed of the control microcomputer is insufficient to achieve close stabilization of the grinding wheel drive motor power. With insufficient response speed, there tends to be a hunting action with the infeed control and typical overshoot and undershoot in infeed rate adjustment. In these situations, quality of the ground workpiece suffers.
U.S. Pat. No. 3,344,560 issued Oct. 3, 1967 illustrates control of the feed rate of a grinding wheel based on changes in deflection of the spindle carrying the wheel. U.S. Pat. No. 3,555,741 issued Jan. 19, 1971 discloses adjusting grinding force in response to signals from a proximity gage sensing spindle deflection resulting from changes in grinding force.